In camera environments (e.g. film, television, live entertainment, sports), a large variety of equipment exists to operate the functionalities of cameras, lighting, and sound. The control and interrelations of these functions determines the qualities of the final imagery and sound perceived by audiences. One such function is camera focus. “Pulling focus” or “rack focusing” refers to the act of changing the lens's focus distance setting in correspondence to a moving subject's physical distance from the focal plane. For example, if an actor moves from 8 meters away from the focal plane to 3 meters away from the focal plane within a shot, the focus puller will change the distance setting on the lens during the take in precise correspondence to the changing position of the actor. Additionally, the focus puller may shift focus from one subject to another within the frame, as dictated by the specific aesthetic requirements of the composition.
This process of adjusting the focus is performed manually by the “First Assistant Camera” (first AC) or “Focus Puller”.
Depending on the parameters of a given shot, there is often very little room for error. As such, the role of a focus puller is extremely important within the realm of a film production; a “soft” image will, in most circumstances, be considered unusable, since there is no way to fix such an error in post-production. One must also consider that an actor may not be able to duplicate his or her best performance in a subsequent take, so the focus puller is expected to perform flawlessly on every take. Because of these factors, some production personnel consider the focus puller to have the most difficult job on set.
Though Focus Pullers can be very skilled, the current process still slows down production due to the complexity and difficulty of the task.
Current film production begins with a blocking rehearsal, in which the various actors' positions are established. During the rehearsal, a camera assistant lays tape marks on the floor at all points where an actor pauses in movement. The actors then leave set to go through hair and makeup, and stand-ins come in to take their places at these various positions for the purposes of lighting, framing, and focus-mark setting.
Once a camera position is established by the director of photography and camera operator, the first AC begins to measure the various distances between the actors' marks and the focal plane of the camera. These distances are recorded in a series of grease pencil/pen marks on the focus barrel of the lens, and/or the marking disc on the follow focus device. Using the stand-ins the marks are checked through the viewfinder and/or the onboard monitor for accuracy. If marks are repositioned in order to provide specific framing desired, the first AC must re-measure/re-set his marks accordingly. Additionally, the first AC may lay down specific distance marks on the floor which will be referenced during the take as actors move between their marks, in order to assist in accurately adjusting the focus to the correct intermediate distances.
When the actors return to set, there is usually a rehearsal for camera in which the focus puller and operator will practice the shot and make sure everything has been set up properly. During a take, the focus puller modifies the focus based on the dialog, movement of the actors or subject, movement of the camera and compensates on the fly for actors missing their marks or any unforeseen movement. In cases where an obstruction prevents the focus puller from seeing all his marks, he may request the second AC to call the marks for him over a 2-way radio during the shot. In some situations, such as on long lenses, wide apertures, very close distances, or any combination of the three, a subject moving even a few millimeters may require immediate and very precise focus correction.
After a take, if the focus puller feels he's made a mistake—be it a timing error, a missed mark, or any other issue which may have rendered some part of the take “soft”, he or she will typically report this to the operator (who most likely noticed the error in the viewfinder) or director of photography, and may ask for another take if another wasn't already planned.
In addition to keen eyesight, reflexes, and intuition, the focus puller's primary tools are a cloth or fiberglass tape measure, steel tape measure, laser rangefinder, and in some cases an on-camera ultrasonic rangefinder which provides a real-time distance readout mounted on the side of the mattebox or camera body. In setups where the focus puller cannot touch the camera, such as on steadicam or crane shots, he or she will use a remote follow focus system, though some focus pullers prefer using a remote system at all times. In any of the above mentioned cases the focus puller is still required to adjust the focus manually during the course of the shot.
The current approach is time consuming, difficult, and highly prone to error. It has long been a technical hurdle in cinematic moving image production and it imposes significant creative constraints on the director as well as increasing the cost of production due to unusable shots, slow setup times and the need for highly skilled and highly paid focus pullers.
Known to the Applicant are semi-automatic focusing systems that depend on lasers, sonar, and facial/object recognition tracking.
These methods are essentially variances of the same approach in that they each sense the “two dimensional plane” of the image and capture depth or distance information for any given area or pixel on that plane. For the most advanced systems, the operator of the system can then choose a point on the two dimensional image, at which time the distance data for that point will then be input to a motor which controls focus adjustment in real-time.
These known methods present some limitations. More particularly, these systems are all “line of sight”. They cannot focus on an object that is not currently visible in the “two dimensional image plane”. The laser system requires an additional operator to target a laser on the desired subject. The facial recognition system will lose track of an object if it turns rapidly, goes off frame or disappears behind another subject or object.
Perhaps most importantly, none of these systems is truly capable of the extreme accuracy required for the most challenging focus tasks, i.e a long focal length with a wide aperture when the subject is moving rapidly and the focus point on the subject is very specific, for example the eye, because for both the LIDaR (Light Detection and Ranging) and laser systems a human operator must keep track of the eye in real-time either by moving a cursor on a screen or by aiming an actual laser. It should also be noted that shining a laser into a person's eye may be undesirable. While the facial recognition system could in theory track and eye, there is a need to provide an increased level of precision and accuracy.
Known to the Applicant are U.S. Pat. No. 5,930,740 (MATHISEN), U.S. Pat. No. 8,448,056 (PULSIPHER), and U.S. Pat. No. 8,562,433 (LARSEN); United States Patent Applications having publication Nos. 2008/0312866 (SHIMOMURA), 2010/0194879 (PASVEER), 2013/0188067 (KOIVUKANGAS), 2013/0222565 (GUERIN), 2013/0229528 (TAYLOR), and 2013/0324254 (HUANG), and Japanese Patent Application having publication No. JP 2008/011212 (KONDO).
Hence, in light of the aforementioned, there is a need for an improved system which, by virtue of its design and components, would be able to overcome some of the above-discussed prior art concerns.